Frequency control apparatus



Sept. 4, 1934. A. GL-:BHARD FREQUENCY CONTROL APPARATUS Original Filed Jan. 8I 1950 2 Sheets-Sheet l Eil :1I T- E INVENTOR. 61,/ Qwfvu),

ATTORNEY QAM/vio Sept. 4, 1934.

L. A. GEBHARD FREQUENCY CONTROL APPARATUS Original Filed Jan. 8, 1930 Elm-m 2 Sheets-Sheet 2 n i" .50 O O Ml l Z j 55a Xy IN VEN TOR.

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ATTORNEY UNTD STATES PATENT FREQUENCY CONTROL APPARATUS Louis A. Gebhard, Washington, D. C., assigner to Wired Radio, Inc., New York, N. Y., a corporatien of Delaware @riginal application January 8, 1930, Serial No. 419,401. Divided and this application etober 15, 1932, Serial No. 638,013

i2 claims. (c1. 1v1-327) My invention relates broadly to frequency conis a fragmentary cross-sectional view through a trol apparatus and more particularly to a Conportion of the temperature controlled cabinet struction of frequency control apparatus which and illustrating the manner in which the rotatamay be selectively adjusted for sustaining elecble frame structure is removably connected with 5 trical oscillations at a number of predetermined terminals within the cabinet structure; and Fig. 60

l'eeiuencies. 4 shows a detailed cross-sectional view of the This application is a division of my application structure of the side walls of the container for Serial No. 419,401, nled January 8, 1930, for Temthe frequency control apparatus. perature control apparatus for frequency control In high frequency transmitters it is necessary devices. to employ a system for maintaining the radiated 65 One of the objects of my invention is to provide energy at a substantially constant frequency. The a construction of frequency control apparatus exciter or master oscillator with which the apwhich includes a temperature controlled housing paratus of my invention is associated. has Jthe and a movable framework therein, the movable frequency thereof controlled by an electrome- 115 framework carrying a multiplicity of electrochanical vibratile element. It is necessary to 70 mechanical vibratile elements having Switching accurately control the temperature of the electromeahe fOr SeleCVelY COhheetIlg any one of the mechanical vibratile element employed in order electromechanical vibratile elements in an electo maintain the selected frequency constant. JlCll Cireu Ol Sustaining high frequency OSCl- Should a plurality of elements having different lations therein. frequency characteristics be employed it is desir- 75 .I

Another object of my invention is toI provide a able to maintain all of the elements at substan- COhStlUCOh Of eflllehel CODTOl elJDElTaUlS tially the same temperature. This usually neceswherein a movable framework is journaled With sitates providing a large space in the transmitter respect to a stationary framework and is pl'ounit for the apparatus containing the tempertaure vided with a plurality oi electromechanical V- controlled elements. 80 bratile elements disposed in a horizontal plane A problem other than available space must be with contact members individual to each of the considered, namely, that the elements must be elements and adapted t0 COCt With aligned COD- maintained at substantially uniform temperature tacts on the stationary framework for the se- Otherwise the change from one element to anleCVe COImeClOh 0f e lleteulal eleCtlOIIleother will not establish the necessary standard 85 cha-nical vibratile element in the circuit Whose frequency, A third consideration is that the elefeiilehey iS t0 be malll-nedments must be readily accessible for interchange A fillthe Obl'et 0f my hvehl'fleh iS t0 DYOVde oi other elements and the elem-ents must be a construction of rotatable mounting frame for a adapted t0 be readily and easily connected to an 35, plurality of electromechanical vibratile elements external circuit and selectively chosen by the 90 with means ioliournang the frame for rotation frequency characteristics of the external circuit. with a temperature controlled cabinet under con- 1 provide a, set of horizontally extending supt-ol of an adjusting device operative from the porting platforms which are carried by a ver- CtelOl 0f the Cebleltically disposed shaft journaled centrally of a 4o Other and further objects of my invention re` framework which is movable into and out of the 95 Side ih the COHSIUCOH e-hd Pilhgelleht Of a cabinet structure. The platforms which are carmultiplicity of electromechanical vibratile elefied by the vertical shaft serve as supports for a ments within a temperature controlled cabinet multiplicity 0f casings, each of which enclose an fel'th 'mere fllly ih the SleeetOh heleelectromechanical vibratile element. The casings luefter fOHOWD-g by 'fe-fel'ehee t0 the eCCOflllefare carried by the platforms in substantially radial 100 11E/ills @Teli/MES, in Wheh alignment with the axes of the casings extending Figli-Te l S flOht View Of the equehcy COhIOl on substantially radial lines through the ver- ;tus with the cabinet structure broken tically disposed rotatable shaft. Contact clips away to ShOW l@he htelel 0f the frequency c011- are arranged adjacent the platforms and electrictrol apparatus, partiallylil'CYOSS-Seotion; Fig. 2 ally insulated from each other to engage the 105 iS e CI'OSS-Se'llehel View when th'fOllgh the tenlterminals on the casings. The contact clips are Pera-ture controlled cabinet on line 2 2 of Fig. so arranged that the casings are individually rel and showing the upper rotatable table which movable from the platforms te permit substitusnpports the casings containing the electrometion of another casing enclosing an electromechanical vibratile elements in plan view; Fig.l 3 chanical Vibratile element. Contact blades are 110 ture of piezo electricy elements.

. ternal .circuit at each adjustment.

provided in electrical connection with the contact clips carried by the platforms. These platforms coact with stationaryV contacts supported adjacent the rotatable platforms. In order that the proper electromechanical vibratile element may be selected and electrically connected in an oscillation circuit, the contact blades projecting from the platforms alternate in their arrangement, that is, the contact blades onk one platform are offset with resp-ect to the contact blades on an' adjacent platform so that the selected electromechanical vibratile element is connected into the control circuit for each angular adjustment of the rotatable platforms.

Fig. 1 of the accompanying drawings shows a front View of the temperature control apparatus of my invention. A portion of the front of container 1 is shown cut away showing discs 1G and 10a, upper plate 15 and lower plate 16 in section. Shaft 11 rests in bearings 13 and 14 provided in plate members 16k and 15 respectively. Like reference. characters are employed throughout the drawings. A resilient arm member 21 is carried by collar 2lb mounted on shaft 1l. Arm 21 carries a semispherical member 21u which engages with detents located in the surface of ring member 22 and as shaft ll-rotates the detents serve as stops to maintain the electrical connection to the ring 22. Ring 22 is secured in position with respect to member 15-by means of screws 22a by which an electrical connection to screw 22a. may be provided in any suitable manner. Bar 8 may be secured to plate members 15 and 15 by means of angle members 9 and screws 8a.. Bevel gears 25 interconnect with shaft 11 and with shaft 26. Shaft 26 extendsV at right angles to shaft 11 and protrudes through the. fron-t side of container1 1. Shaft 25 may be en-tirely of suitable insulating material the purpose of which is to prevent any pronounced transfer of heat between the inside and outside of container l, or the shaft 26. may be brokenl by a suitable insulating coupling at the position where the shaft 26y passes through the walls of the cabinet contacts 23 and 24 in engagement with brushes 6. Discs 10 and 10aI are shown in section comprising a carrier for elements 2- and, 201` respectively. As shown, ele-v ments 2V and 2a are piezo electric crystals contained in individual holders which are removable.

- Clips 19v and 20 connect to the two contact lugs carried by the holders'and establish electrical connection. to the crystal elements, A brush 21e mounted on collar 21h extends radially opposite arm 21 to form a movable electrical contact withv ring 22. Part of the surface of ring 22 contains the; detents for receiving the member 21a while the remainder of the surface of the'ring 22v is emplayedl for providing contact with brush 21e.

While 'piezo electric crystal elements have been y referred to, it is obvious that other elements-such.

as magnetostriction rods may be employed. Thenecessity for main-taining the temperature of magnetostriction rods at a. constant value, is as important as maintaining constant the temperarom; the outside of container 1 the selection of different eiementsmayV be controlled' by dial and knob 52 which is, carried on shaft 261 Dial and knob521alsoindicates: the element which is connected tothefex- With. a permanent selection of elements as in a transmitting system operating on certain frequencies., dia-l 52` may be calibrated in kilocyelesf. Door 3f?. is shownv inV section.V The edges of doorfB' are recessed asf shown in'lig'. 1 at 361 Hinges 38v are provided at the left of the door and a latch is provided at the right. This latch is not shown in the accompanying drawings but is of suitable design to force door 3'? to form a very close i'lt with the recessed edges of the front wall of container 1. Where the hinged door carries a heater element, there are provided suitable flexible connectors dil-6l between the heating element in the cabinet walls and the terminals 62--63 of the heating clement carried by the hinged door for completing the electrical circuits. The outermost layer 27 of suitable insulating material is here shown in section, exposing layer 28 upon which the heater element is wound. The heater wire is wound in notches 28a disposed in the opposite ends of layer 28 and extends across the layer as illustrated. The top and bottom turns of the heater Wire are secured in the notches 26a as yshown at 29a, while the principal portions of the heater wire are disposed on the inner side of layer 28. Between layer 28 and the distributing layers of metal, previously referred to, a layer 29 of suitable heat conducting and electrical insulating material is provided.

' Tl'lermometerv 40 is shown in section; a clamping member 42 securing the body of the thermoineter the proper position and the graduated temperature scaleY or upstanding portion 41 in a vertical position. The. body cf thermometer 4Gy extends through the front panel of container 1V. The'upstanding portion 4l is calibrated and indicates the temperature inside the container: The mercury type thermostat 32, also previously ren ferred to, is shown in side elevation. Y Distributing layers 31 and 31a of aluminum or other suitableV metal are shown separated thereby providing an. opening for the body of the thermostat. The control portion or stem extends through bushing 32h which is threaded into the insulating layers on the top side of container 1. Lower plate member 15 forming part of the unit framework is` elevated from the bottom of container 1 by members 35. Screws 5l are provided to secure the heat insulating layer 27 to' the other layers of the container. Screws 59' extend from layer 26through tolayer 34. The heater element is wound in notches 28a provided in layer 28. Screw holes a are shown through which the screws 51 pass when the outermost panel 2'7 is in place. By removing the four screws indicated, access is had to the heater element for adjustment, repair or replacement. This feature is very desirable since it is often times necessary to adjust the length of the heater wire employed to provide equalityof temperature inV all sides of the container 1. A and B indicate bindingA posts which are employed in a mccliicationof my invention. The hea-ter element is separated near the binding posts A and B to avoid any short circuit of the heater elements. Dial- 52 is shown carried on shaft 26 at the fronty of the container. By means of dial 52 selection of the desired piezo electric element is made possibleV as aforementioned in connection with Fig. 1.r The `upstanding stem 41 of mercury type thermometer 40 is positioned with in Figs. 1, 2 and 4 is secured by bushing 32h in the 1 Y f wall of. the cabinet structure. n VThe thermostat socket is'constru'cted by causing a bulge in the distributing layers 3l and 31a which receives the thermostat as has been described heretofore.

Fig.V 2: is; a top plan view in part section show- This thermometer indiist ing the apparatus of my invention. The electromechanical vibratile elements 2 are mounted on a framework. contained within container 1. A stationary contact member 6 is carried by a contact arm 7 which is secured to bar 8 by means of screw 7a. Bar 8 is supported by an angle 9. Elements 2 have associated contact lugs which engage with clips 19 and 20. Clips 20 are positioned on an annular metallic member 12 by screws 12a.. Member 12 is in turn supported by shaft 11 which is of metal. Elements 2 rest upon a disc 10 which may be of insulating material. Near the periphery of disc 10 contact clips 19 are provided for retaining the other contact lug of elements 2. The electrical connection to elements 2 is therefore provided by connecting to contacts 23 and shaft 11. Disc 10 may be of metal, in which case clips 19 and contacts 23 would be supported by but suitably insulated from disc 10. Disc 10 is supported from shaft 11 by member l2 and is movable therewith. A second disc 1Go. is also carried by shaft 11, which disc is similar to disc 10 and carries a plurality of mechanically vibratile elements 2a. Disc 10a and one of the elements 2a is shown in the broken section of disc 10. Shaft 11 is supported in suitable bearings shown in Fig. 1 and is rotated by shaft 26 under control of knob 52 to which dial 52a is attached. Shaft 26 has a bevel gear 25 thereon intermeshing with a similar gear on shaft 11. The revolving framework carrying the elements 2 and 2a and the stationary contact assembly are all positioned with respect to a frameworl; comprising a lower plate member i6 and upper plate member 15. Rods 1'? extend between the lower plate member 16, and the upper plate member 15. Inasmuch as Fig. 2 is a section through the cabinet below the upper plate member l5, only the lower plate member 16 is shown aithough the arrangement of the plate members is clearly shown in Fig. 1.

Container' 1 is cube shaped which is satisfactory for most purposes. The ideal shape would bc spherical. However, manufacture of this design is not wholly practicable. The nearest approach is the cubical shaped construction employed in accordance with my invention, All six sides or" the cube shaped container are made up of laminated sheets of material. The outermost layer 27 is of suitable insulating material. The second layer 2S is of insulating material upon which the heater wire 29a is wound. Next is a thin layer of mica 29h or other electrical insulating but heat conducting material. This layer is employed primarily to electrically insulate the heater from the next two layers 31 and 31a which are of metal such as aluminum, and which act as heat distributing layers. A filler layer 29 is provided which substantially surrounds the thin layer of mica 29h and heater wire 29a, thus equalizing the thickness of the several layers at any position through the walls. Layer 29 may be made of any suitable heat insulating material. Next is a layer of asbestos 33 or similar material which is adjacent to a layer of copper Any desired number of l alternate layers of asbestos 33 and copper 33a may be provided between the distributing layers 31, 310l and the inside layer 34 of the container which may be of aluminum or other suitable material for lining the interior of the container. The distributing layers 3l, 31a are bulged as shown at 32aJ providing an opening for a mercury type thermostat 32. To permit access to the mechanically vibratile elements, a door 37 is provided in the front side of container 1. The opening for the door is of special design, the edges being stepped as shown at 36. By recessing the edges in this manner a very efcient heat insulating joint can be had. Leakage of air to the inside of the compartment or vice versa is almost entirely eliminated. Thermometer 40 is provided to indicate the temperature of the inside of the compartment. Thermometer 40 has an upturned portion 41 at right angles to body 40. r)This permits visual indication of the temperature scale. Thermometer 40 extends through an opening in the front oi container 1 and is positioned adjacent the front by means of clamping screws 42.

Fig. 3 shows further details of the temperature controlled apparatus of my invention. The illustration shows a sectional View taken through the side wall of the container showing particularly the top and right side of the container. t is sometimes desired to remove the entire rotatable frame-work which carries the mechanically vibratile elements. As heretofore mentioned, the elements associated with the adjusting mechanism and contact members are mounted on a framework consisting of an upper and lower plate member and supported by rod members extending vertically as shown in Figs. 1 and 2. rihe upper plate nember 15 is here shown carrying contact member 43 supported by upstanding members 55. Contact member 43 consists of two laminated spring metal arms. Positioned on the top of container 1 there is provided an insulating member 45 which carries contact member 44. Contact members 43 and 44 may be properly called plug and jack respectively. is electrically connected to the metallic body 45 of binding post 8 by connector An insulating body 46a surrounds the metallic body 46, thereby electrically insulating the same from the metallic distributing layers. nection is established between terminal 43a oi contact 43 to the stationary contacts or supporting bar 8 shown in Fig. 1. By referring to Fig. 1 it may be seen how such connection can be provided by connection to screw 8a. An arrangement similar to that shown in l-Tig. 3 is also provided for establishing electrical connection to the other side of the mechanically vibratile element, which as heretofore described is provided for metallic annular shaped member 22. In the lat- )if ter connecting arrangement a contact member similar to contact 43 is electrically connected to annular shaped ring 22 or to the mounting screw 22a which holds the same to upper plate member 15. This contact arrangement is provided so that it is possible, by removing the front wall of container 1, the entire framework carrying the vibratile elements may be removed from the housing 1, thereby pennitting access to the unit in its entirety for repair, replacement and the like.

Fig. 4 shows a section of the wall of container 1 and illustrates the method of mounting different mernl ers on the container'. The layers as previously mentioned insulating layers 27 and 28, heat conducting and electrical insulating g;

layer 29, heat distributing layers 31 and 31a, alternate layers of asbestos or the like and suitable metal such as Copper 33 and 33a respectively and the inside lining 34 of suitable metal such as aluminum. The essential feature shown in this illustration is that no screws extend through the entire wall of the container. Such screws if extended through all of the layers would offer a path of relatively high temperature conductivity. For this reason the screws are arranged in An electrical con- Contact member 44 a manner somewhat as shown, wherein screw 51 extends part way through the wall, namely through the layers 27, 28, 29 and threaded into the distributing layers 31, 31a. The member 58 is secured by a separate screw 50 which extends through layers 28, 29, 31,- 31a, S3, 33a and 34. A countersunk screw as shown may be employed in the latter instance. Where it is not desired to mount a member' 58 on the inside of the container, screw 50 may be threaded into the innermost layer 34. By fastening the several layers together in this manner, any apparatus desired may be mounted directly upon metallic layer 3ft. The screws may be distributed on the several wallsof container 1 as desired depending upon the rigidity sought.

By referring to Figs. l and 2, an understanding of the operation and the advantageous features will appear. The elements 2 on the upper platform 1o and the elements 2a on the lower platform 10a are arranged to b'e connected to the external circuit in alternate order. rlhis may be accomplished by having the elements 2a positioned offset as shown in Fig. 2 or the equivalent, the contact members offset in' like manner.

Thestationary contact members 6 carried by bar 8 may be suitably arranged 'to connect to elements 2 and 2a in alternate order when. elements Zand 2a are positioned immediately under each other insteadof the offset positioning as shown in 2. Any number of discs similar 'to discs 10 and lila may be employed arranged one over the other as shown. The elements or connection to the elements may be' from rst one disc and then the next in successive order which may be effected by placing the rotating contacts to the elements in echelonic formation with respect to the different discs or the stationary contacts be arranged in such a manner if it is desired to place the elements in lin-e one over the other on the respective discs. The discs should be of sumcient number or proportionally spaced on shaft l1 to occupy the area of a cube as nearly as possible. Thus if four discs of diameter d are ernployed the vertical dimension'- occupied by all the discs should be 03 and the separation between the discs divided accordingly.

r1he various layersconstituting the sides of container 1 are interleaved at the corners as shown in Fig. l of the accompanying drawings. The heater elements in.Y the six sides are connected in series to permit the same current to pass through each7 element. Minor irregularities in the heating canV be controlled by adjusting the length of the wire constituting the heater element in each of the sides. The container 1 in its entirety is mounted on the front panel of the radiov transmitter or apparatus.

fr door should beprovided in` the front panel of the transmitter corresponding to the position of door 37 by means of which access to the mechanically vi'o'ratile elements may be had. A' suitable window should alsobe provided in the front panel to permit sighting thermometer 41. Thermostat 32 is located adjacent the heater element provided in container 1 and connected with a suitable source of electrical energy for controlling the current to the heater. rIfne framework supporting the rotating platforms is secured to the' front panel and may be drawn out horizontally in the process of disassembly which disengages the contacts i4 and 431, permitting withdrawal of the equipment in order that repairs or mechanical adjustment may be made` to the mechanism. Screws are provided through the laminations 28, 29, 31, 31a, 33, 33a, and 34 for binding the front group of layers toenable the front section to be removed orinserted as a unit. Access to any one of the -crystals is readily obtained by rotating the platforms to bring the desired crystal to a position at the front of the cabinet from which it may be inserted or removed.

The apparatus of my invention may be mounted with respect to a panel of a radio transmitter with a suitable window cut in the panel to permit sighting the scale of the thermometer 41 therethrough. Y

Shaft 26 projects through the front of panel 64, the knob 52 and dial being secured to the end of shaft 26. The calibrations on the dial are registered with a calibration on panel 64 to enable the apparatus to be shifted to the desired frequ-ency.

Many modifications of my invention are possible and it is to be understood that the embodiments of my invention are not to be restricted by the foregoing specication or by the accompanying drawings but that changes may be made within scope of the appended claims without de parting from the spirit of my invention.

What I claim as new and desire to secure by Letters atent of the United States is as follows:

1. Frequency control apparatus comprising in combination a container of substantially cube contour, a' supporting frame positioned in said container, a rotary framework journaled in said Aupporting frame, said rotary frameworl comprising a plurality of horizontally kdisposed disl's ially arranged on a vertically positioned shaft and a plurality of electromechanically vibratile elements carried by said disks, contact members on said disks connected with said elements, contact members on said supporting frame, said first mentioned contact members being adapted to be selectively' engaged with the second mentioned contact members carried by said supporting frame.

2. Frequency control apparatus comprising in combination a container, a stationary framework mounted in said container, a movable framework Y.supported by said stationary framework, said movable framework carrying a plurality of electromechanically vibratile elements disposed in a horizontal plane, contact members individual to each of said elements, sets of stationary contacts mounted on said stationary framework, the contact members on said movable framework being adapted to be selectively connected with the stationary contacts carried by said stationary framework. y

3. Frequency control apparatus for signaling systems comprising in combination a container having enclosed therein a rotatable framework consisting of a plurality of platforms arranged one over the other in separate horizontal planes, a plurality of electromechanically vibratile elements mounted on each of said platforms, contact members carried by said platforms and individually connected'with each of said elements, and sets of stationary contacts within said container in alignment with the contacts on saidV platforms. v

4. Frequency control apparatus for signaling systems comprising in combination a' container having enclosed therein a rotatable framework consisting of a plurality of platforms arranged one ov r the other in horizontal planes, a plurality of electromech'a'nicallyV vibratile elements carried by each of said platforms, contact members carried by said'platformsand individually connected with said elements on said platforms, said contact members alternating in position one with respect to another on the respective platforms, sets of stationary contacts Within said container in alignment with the contacts on said platforms whereby connection of said elements to an external circuit is completed alternately through an element carried by different platforms.

5. Frequency control apparatus comprising a cabinet structure, a frame mounted Within said cabinet structure, a vertically dis-posed shaft member `iournaled in said frame, a horizontally disposed platform carried by said shaft member, a multiplicity of frequency control devices carried by said platform, a contact member carried by said platform individual to each of said frequency control devices, contact members carried by said frame structure, and means projecting through said cabinet structure for rotating said shaft and imparting movement to said platform for switching said frequency control devices selectively into engagement with the contact members on said frame structure in step by step operations.

6. Frequency control apparatus comprising a cabinet structure, a frame mounted within said cabinet structure, a vertically disposed shaft member journaled in said frame, a horizontally disposed platform carried by said shaft member, a multiplicity of frequency control devices carried by said platform, a Contact member carried by said platform individual to each of said frequency control devices, contact members carried by said frame structure, a gear on said shaft, a control shaft projecting through said cabinet structure normal to the aforesaid shaft, a gearing connection between said shafts interiorly of said cabinet structure whereby rotation of said control shaft exteriorly of said cabinet structure imparts corresponding movement to said platform interiorly of said cabinet structure for selectively connecting or disconnecting contacts individual to each of said frequency control devices with the contacts on said frame structure.

7. Frequency control apparatus comprising a supporting container, terminal clips mounted within said container, a movable framework slidable into and removable from said container, contacts carried by said framework adapted to electrically connect with the terminal clips within said container, a rotatable support journaled with respect to said framework, a plurality of electromechanical vibratile elements mounted on said rotatable support and having contact blades adapted to register with contact members on said framework, and means operative from the exterior of said housing for rotating said rotatable support to a position where said electromechanical vibratile element is selectively connected with a control circuit.

8. Frequency control apparatus comprising a cabinet structure, terminal clips in said cabinet structure, a frame insertable into and removable from said cabinet structure, terminals carried by said frame adapted to electrically connect with the terminal clips within said cabinet structure, a rotatable shaft journaled in said frame, platforms carried by said rotatable shaft in spaced relation, electromechanical vibratile elements supported on said platforms, switch blades individual to each of said electromechanical vibratile elements, contacts carried by said frame, and means operative from the exterior of said cabinet structure for angularly shifting said platforms for selectively connecting a predetermined electromechanical vibratile element with a control circuit through the contact clips on said frame.

9. Frequency control apparatus comprising a cabinet structure, a support Within said cabinet structure, a vertically extending shaft journaled in said support, a plurality of platforms spaced one above another carried by said shaft, sets of contact clips disposed radially on each of said platforms, casings each enclosing an electromechanical vibratile element supported on said platforms and having terminals electrically connected with said contact clips, switch blades individual to certain of said contact clips and movable in the path of contact clips carried by said support, and means exterior of said cabinet for angularly shifting said shaft for selectively connecting a predetermined electromechanical vibratile element with the Contact clips on said support.

l0. In a device of the class described, a rotary mounting, a plurality of removable crystal holding units supported by said mounting and symmetrically disposed thereon, each of said crystal holding units having a pair of contact lugs, said mounting having a plurality of Contact clips engageable with said lugs, a housing for said mounting, said housing having at least one pair of electrical binding posts for connecting one of said crystal holding units into a given circuit, and stationary connectors electrically connected with said binding posts for connecting said contact clips selectively, whereby, upon rotation of said mounting, any desired crystal holding unit may be introduced into said given circuit.

l1. Frequency control apparatus comprising a plurality of mechanically vibratile elements, an individual container for each element having contact lugs exterior thereof for connecting said element into a given circuit, a rotatable framework for supporting said containers in symmetrical arrangement about the axis thereof, a housing in which said rotatable framework is carried, said housing having binding posts extending through a wall thereof, and means for selectively connecting said binding posts with the contact lugs of any desired individual container, said means being operable in accordance with the rotation of said framework.

12. A device in accordance with claim 1l in which said rotatable framework is provided with a plurality of platforms having contact clips secured thereto and adapted for engagement with the contact lugs of said individual containers whereby each of said containers is held in position on said platforms.

LOUIS A. GEBHARD. 

